- Palladium-catalyzed synthesis of arylamines from diphenyliodonium tetrafluoroborate and secondary amine
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The hetero-cross coupling reaction of diphenyliodonium tetrafluoroborate with secondary amine in the presence of LiNTMS2 or NaOtBu as base, Pd2(dba)3?CHCl3 as catalyst, and tri-o-tolylphosphine as ligand afforded arylamines at room temperature under mild conditions.
- Kang, Suk-Ku,Lee, Hong-Woo,Choi, Won-Kyu,Hong, Ryung-Kee,Kim, Jae-Sun
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- Phosphines with N-Heterocyclic Boryl-Substituents: Ligands for Coordination Chemistry and Catalysis
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Boryl-substituted phosphines NHB–P(R)Ph (R = H, Ph, NHB = N-heterocyclic boryl substituent) react with Fe2(CO)9 to give isolable Fe(CO)4 complexes, two of which were characterized by single-crystal XRD studies. The electronic and steric properties for a series of the boryl phosphines were further assessed by evaluation of TEPs for in-situ formed complexes [RhCl(NHB–PR1R2)(CO)2] (R1, R2 = H, Ph, Me, NMe2), and calculations of buried volumes for Fe(CO)4 complexes. The results imply that the NHB-phosphines exhibit due to their conformational flexibility some variability in their steric bulk, and that some specimens may exhibit similar electron releasing power and steric demand as tBu3P. Studies of the amination of bromobenzene with 2,6-diisopropylaniline confirmed that these properties can be exploited to promote Pd-catalyzed C–N cross coupling reactions, and that formal replacement of a phenyl by a NHB substituent in the auxiliary phosphine has a beneficial effect on catalyst performance.
- Kaaz, Manuel,Locke, Ralf J. C.,Merz, Luisa,Benedikter, Mathis,K?nig, Simon,Bender, Johannes,Schlindwein, Simon H.,Nieger, Martin,Gudat, Dietrich
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- Synthesis, characterisation and reactivity of copper(I) amide complexes and studies on their role in the modified Ullmann amination reaction
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A series of copper(I) alkylamide complexes have been synthesised; copper(I) dicyclohexylamide (1), copper(I) 2,2,6,6-tetramethylpiperidide (2), copper(I) pyrrolidide (3), copper(I) piperidide (4), and copper(I) benzylamide (5). Their solid-state structures and structures in [D6]benzene solution are characterised, with the aggregation state in solution determined by a combination of DOSY NMR spectroscopy and DFT calculations. Complexes 1, 2 and 4 are shown to exist as tetramers in the solid state by X-ray crystallography. In [D6]benzene solution, complexes 1, 2 and 5 were found by using 1H DOSY NMR to exist in rapid equilibrium between aggregates with average aggregation numbers of 2.5, 2.4 and 3.3, respectively, at 0.05 M concentration. Conversely, distinct trimeric, tetrameric and pentameric forms of 3 and 4 were distinguishable by one-dimensional 1H and 1H DOSY NMR spectroscopy. Complexes 3-5 are found to react stoichiometrically with iodobenzene, in the presence or absence of 1,10-phenanthroline as an ancillary ligand, to give arylamine products indicative of their role as potential intermediates in the modified Ullmann reaction. The role of phenanthroline has also been explored both in the stoichiometric reaction and in the catalytic Ullmann protocol.
- Sung, Simon,Braddock, D. Christopher,Armstrong, Alan,Brennan, Colin,Sale, David,White, Andrew J.P.,Davies, Robert P.
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- L-Proline N-oxide dihydrazides as an efficient ligand for cross-coupling reactions of aryl iodides and bromides with amines and phenols
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A novel catalytic system based on L-proline N-oxide/CuI was developed and applied to the cross-coupling reactions of various N- and O- nucleophilic reagents with aryl iodides and bromides. This strategy featured in the employment of an-proline derived dihydrazides N-oxide compound as the superior supporting ligand. By using this protocol, a variety of products, including N-arylimidazoles, N-arylpyrazoles, N-arylpyrroles, N-arylamines, and aryl ethers, were synthesized with up to 99% yield.
- Ding, Zhiqiang,Nie, Nan,Chen, Tian,Meng, Lingxin,Wang, Gongshu,Chen, Zhangpei,Hu, Jianshe
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supporting information
(2020/12/21)
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- Iridium and bis(4-nitrophenyl)phosphoric acid catalysed amination of diol by hydrogen-borrowing methodology for the synthesis of cyclic amine: Synthesis of clopidogrel
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The borrowing hydrogen method is an environmentally benign process for the synthesis of amines, as H2O is the side product. A new green process for the amination of diol by [Ir] catalyst 15 and bis(4-nitrophenyl)phosphoric acid for the synthesis of cyclic amine is reported. This method was successfully applied for the synthesis of antiplatelet drug clopidogrel.
- Swain, Sharada Prasanna,Shri, Om,Ravichandiran
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- Iodine-Mediated Coupling of Cyclic Amines with Sulfonyl Hydrazides: an Efficient Synthesis of Vinyl Sulfone Derivatives
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An efficient iodine-mediated coupling of cyclic amines with sulfonyl hydrazides is reported. This transformation opens a new route to the synthesis of vinyl sulfones derivatives, which is a common structural motif in natural products and pharmaceuticals. Tentative mechanistic studies suggest that this reaction is likely to involve a radical process.
- Rong, Xiaona,Guo, Jingwen,Hu, Zheqi,Huang, Lehao,Gu, Yugui,Cai, Yuepiao,Liang, Guang,Xia, Qinqin
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supporting information
p. 701 - 708
(2020/12/30)
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- Organic photoredox catalytic α-C(sp3)-H phosphorylation of saturated: Aza -heterocycles
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A metal-free C(sp3)-H phosphorylation of saturated aza-heterocycles via the merger of organic photoredox and Br?nsted acid catalyses was established under mild conditions. This protocol provided straightforward and economic access to a variety of valuable α-phosphoryl cyclic amines by using commercially available diarylphosphine oxide reagents. In addition, the D-A fluorescent molecule DCQ was used for the first time as a photocatalyst and exhibited an excellent photoredox catalytic efficiency in this transformation. A series of mechanistic experiments and DFT calculations demonstrated that this transformation underwent a sequential visible light photoredox catalytic oxidation/nucleophilic addition process.
- Yi, Ming-Jun,Xiao, Teng-Fei,Li, Wen-Hui,Zhang, Yi-Fan,Yan, Pen-Ji,Zhang, Baoxin,Xu, Peng-Fei,Xu, Guo-Qiang
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supporting information
p. 13158 - 13161
(2021/12/16)
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- NiFe2O4@SiO2@ZrO2/SO42-/Cu/Co nanoparticles: A novel, efficient, magnetically recyclable and bimetallic catalyst for Pd-free Suzuki, Heck and C-N cross-coupling reactions in aqueous media
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The novel heterogeneous bimetallic nanoparticles of Cu-Co were synthesized based on magnetic nanoparticles, and the magnetic nanocatalyst was characterized by XRD, FE-SEM, EDX mapping, BET, TEM, HRTEM, FTIR, TGA, and VSM. This catalyst was successfully applied as a recyclable magnetically catalyst in Heck, Suzuki, and C-N cross-coupling reactions with various aryl halides (iodides, bromides, and chlorides as challengeable substrates), with olefins, phenylboronic acid, and amines, respectively. We considered the rise of synergetic effects from the different Lewis acid and Br?nsted acid sites present in the catalyst. The catalyst was synthesized with cheap, available materials and a simple synthesis method. The catalyst can be separated easily using an external magnet. It was recycled for more than ten runs without a sensible loss of its catalytic activity, and no significant leaching of the Cu and Co quantity was observed. The significant benefits of the method are high-level generality, simple operation, and there are no heavy metals and toxic solvents. This is a quick, easy, efficacious and environmentally friendly protocol, and no by-products are formed in the reaction. These features make it an appropriate practical alternative protocol. In comparison with recent works, the other advantage of this catalyst is the synthesis of a wide variety of C-C and C-N bond derivatives (more than 40 derivatives). The other significant advantage is the low temperature of the reaction and the use of the least possible amount of the catalyst (0.003 g). The efficiency was good to excellent and the catalyst selectivity has been high. We aspire that our study inspires more interest to design novel catalysts based on using low-cost metal ions (such as cobalt and copper) in the cross-coupling reactions. This journal is
- Alavi G., Seyyedeh Ameneh,Nasseri, Mohammad Ali,Kazemnejadi, Milad,Allahresani, Ali,Hussainzadeh, Mahdi
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p. 7741 - 7757
(2021/05/13)
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- Mediator-Enabled Electrocatalysis with Ligandless Copper for Anaerobic Chan-Lam Coupling Reactions
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Simple copper salts serve as catalysts to effect C-X bond-forming reactions in some of the most utilized transformations in synthesis, including the oxidative coupling of aryl boronic acids and amines. However, these Chan-Lam coupling reactions have historically relied on chemical oxidants that limit their applicability beyond small-scale synthesis. Despite the success of replacing strong chemical oxidants with electrochemistry for a variety of metal-catalyzed processes, electrooxidative reactions with ligandless copper catalysts are plagued by slow electron-transfer kinetics, irreversible copper plating, and competitive substrate oxidation. Herein, we report the implementation of substoichiometric quantities of redox mediators to address limitations to Cu-catalyzed electrosynthesis. Mechanistic studies reveal that mediators serve multiple roles by (i) rapidly oxidizing low-valent Cu intermediates, (ii) stripping Cu metal from the cathode to regenerate the catalyst and reveal the active Pt surface for proton reduction, and (iii) providing anodic overcharge protection to prevent substrate oxidation. This strategy is applied to Chan-Lam coupling of aryl-, heteroaryl-, and alkylamines with arylboronic acids in the absence of chemical oxidants. Couplings under these electrochemical conditions occur with higher yields and shorter reaction times than conventional reactions in air and provide complementary substrate reactivity.
- Walker, Benjamin R.,Manabe, Shuhei,Brusoe, Andrew T.,Sevov, Christo S.
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supporting information
p. 6257 - 6265
(2021/05/07)
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- Synthesis of N-heterocyclic carbene-Pd(II)-5-phenyloxazole complexes and initial studies of their catalytic activity toward the Buchwald-Hartwig amination of aryl chlorides
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Three new N-heterocyclic carbene (NHC)-Pd(II) complexes using 5-phenyloxazole as the ancillary ligand have been obtained in moderate to good yields by a one-pot reaction of the corresponding imidazolium salts, palladium chloride and 5-phenyloxazole under mild conditions. Initial studies showed that one of the complexes is an efficient catalyst for the Buchwald-Hartwig amination of aryl chlorides with various secondary and primary amines under the varied catalyst loading of 0.01-0.05 mol%, thus it will enrich the chemistry of NHCs and give an alternative catalyst for the coupling of challenging while cost-low aryl chlorides.
- Zhang, Zhi-Mao,Xu, Yu-Ting,Shao, Li-Xiong
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- Nickel-Catalyzed Amination of Aryl Chlorides with Amides
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A nickel-catalyzed amination of aryl chlorides with diverse amides via C-N bond cleavage has been realized under mild conditions. A broad substrate scope with excellent functional group tolerance at a low catalyst loading makes the protocol powerful for synthesizing various aromatic amines. The aryl chlorides could selectively couple to the amino fragments rather than the carbonyl moieties of amides. Our protocol complements the conventional amination of aryl chlorides and expands the usage of inactive amides.
- Li, Jinpeng,Huang, Changyu,Wen, Daheng,Zheng, Qingshu,Tu, Bo,Tu, Tao
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p. 687 - 691
(2021/01/09)
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- Synthesis method of 1-(4-bromophenyl) piperidine
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The invention discloses a preparation method of 1-(4-bromophenyl) piperidine, and belongs to the technical field of medical intermediates. Bromobenzene and piperidine are used as raw materials and react with potassium tert-butoxide or sodium tert-amyl alcohol in sulfolane in a heating mode to obtain N-phenyl piperidine; and then in the presence of a catalyst tetra-n-butyl tetraphenyl ammonium borate, a bromination reagent is added to react to obtain the 1-(4-bromophenyl)piperidine. The method is few in reaction steps, simple and convenient to operate and relatively high in yield, and a new path is provided for synthesis of the 1-(4-bromophenyl) piperidine.
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Paragraph 0022-0027
(2021/04/14)
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- Highly Chemoselective Deoxygenation of N-Heterocyclic N-Oxides Using Hantzsch Esters as Mild Reducing Agents
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Herein, we disclose a highly chemoselective room-temperature deoxygenation method applicable to various functionalized N-heterocyclic N-oxides via visible light-mediated metallaphotoredox catalysis using Hantzsch esters as the sole stoichiometric reductant. Despite the feasibility of catalyst-free conditions, most of these deoxygenations can be completed within a few minutes using only a tiny amount of a catalyst. This technology also allows for multigram-scale reactions even with an extremely low catalyst loading of 0.01 mol %. The scope of this scalable and operationally convenient protocol encompasses a wide range of functional groups, such as amides, carbamates, esters, ketones, nitrile groups, nitro groups, and halogens, which provide access to the corresponding deoxygenated N-heterocycles in good to excellent yields (an average of an 86.8% yield for a total of 45 examples).
- An, Ju Hyeon,Kim, Kyu Dong,Lee, Jun Hee
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supporting information
p. 2876 - 2894
(2021/02/01)
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- Green tea extract–modified silica gel decorated with palladium nanoparticles as a heterogeneous and recyclable nanocatalyst for Buchwald-Hartwig C–N cross-coupling reactions
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A novel green tea extract–encapsulated silica gel decorated with in situ–generated Pd nanoparticles is reported as an efficient, green heterogeneous catalyst in the Buchwald-Hartwig C–N cross-coupling reaction. It was characterized by several analytical techniques. Thereafter, a wide range of aryl amines were synthesized in good to excellent yields by reaction of different substituted aryl halides and secondary amines over the catalyst. The material is sufficiently stable and could be used at least six times in a model Buchwald-Hartwig reaction without noticeable change in its catalytic activity. Heterogeneity of the catalyst was examined by a hot filtration test.
- Veisi, Hojat,Tamoradi, Taiebeh,Karmakar, Bikash,Hemmati, Saba
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- Cu(I)-anchored polyvinyl alcohol coated-magnetic nanoparticles as heterogeneous nanocatalyst in Ullmann-type C–N coupling reactions
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In this paper, the preparation of a novel magnetic nanocatalyst (Fe3O4?PVA/CuCl) is described, which involves coating of polyvinyl alcohol (PVA) onto the surface of Fe3O4 nanoparticles and its subsequent coordination with CuCl catalyst. The nanocatalyst was characterized by various analytical methods, including Fourier-transform infrared, X-ray diffraction, inductively coupled plasma spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy, vibrating-sample magnetometry, and EDX elemental mapping. Moreover, the nanocatalyst was efficiently used in the N-arylation of amines via the formation of a carbon–nitrogen bond between the aryl halides and amines by Ullmann-type coupling reactions. The catalyst was sufficiently stable and can be reused for at least seven times in a model Ullmann reaction without remarkable alteration in its catalytic behavior. Heterogeneity of the catalyst was investigated by a hot filtration test.
- Ahany Kamangar, Sheida,Hashemi Salehi, Mirmehdi,Hekmati, Malak,Hemmati, Saba,Yousefi, Mohammad
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- Integrating CuO?Fe2O3 Nanocomposites and Supramolecular Assemblies of Phenazine for Visible-Light Photoredox Catalysis
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A photoredox catalytic ensemble consisting of CuO-Fe2O3 nanocomposites and oligomeric derivative of phenazine has been developed. The prepared system acts as an efficient photoredox catalyst for C?N bond formation reaction via SET mechanism under ‘green’ conditions (aerial environment, mixed aqueous media, recyclable), requiring less equivalents of base and amine substrate. The present study demonstrates the significant role of supramolecular assemblies as photooxidants and reductants upon irradiation and their important contribution towards the activation of the metallic centre through energy transfer and electron transfer pathways. The potential of oligomer 4: CuO-Fe2O3 has also been explored for C?C bond formation reactions via the Sonogashira protocol.
- Kaur, Lovjot,Deol, Harnimarta,Kumar, Manoj,Bhalla, Vandana
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supporting information
p. 892 - 898
(2020/03/04)
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- Redox-Selective Iron Catalysis for α-Amino C-H Bond Functionalization via Aerobic Oxidation
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Single-electron oxidation and α-deprotonation of tertiary anilines using Fe(phen)3(PF6)3 afford α-aminoalkyl radicals, which can be coupled with electrophilic partners to afford various tetrahydroquinolines. Mechanistically, the Fe(phen)n 2+/3+ catalytic cycle is maintained by O2 or a TBHP oxidant, and the presence of the oxygen bound iron complex, Fe(III)-OO(H), was elucidated by electron paramagnetic resonance and electrospray ionization mass spectrometry. This redox-selective nonheme iron catalyst behaves similarly to bioinspired heme iron catalysts.
- Hwang, Joon Young,Ji, A. Young,Lee, Sang Hyeok,Kang, Eun Joo
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supporting information
p. 16 - 21
(2019/11/11)
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- Catalyst-free photodecarbonylation ofortho-amino benzaldehyde
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It is almost a consensus that decarbonylation of the aldehyde group (-CHO) needs to not only be mediated by transition metal catalysts, but also requires severe reaction conditions (high temperature and long reaction time). In this work, inspired by the “conformational-selectivity-based” design strategy, we broke this consensus and discovered a catalyst-free photodecarbonylation of the aldehyde group. It revealed that decarbonylation can be easily achieved with visible light irradiation by introducing a tertiary amine into theortho-position of the aldehyde group. A diverse array of tertiary amines is tolerated by our photodecarbonylation under mild conditions. Furthermore, the (QM) computations of the mechanism and the experiments on well-designed special substrates revealed that our photodecarbonylation depends on the conformational specificity of the aldehyde group and tertiary amine, and occurs through an unusual [1,4]-H shift and a subsequent [1,3]-H shift.
- Li, Lamei,Wang, Songping,Wei, Wentao,Yan, Ming,Zhou, Jingwei
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supporting information
p. 3421 - 3426
(2020/06/25)
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- Leaving Group Ability in Nucleophilic Aromatic Amination by Sodium Hydride-Lithium Iodide Composite
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The methoxy group is generally considered as a poor leaving group for nucleophilic substitution reactions. This work verified the superior ability of the methoxy group in nucleophilic amination of arenes mediated by the sodium hydride and lithium iodide through experimental and computational approaches.
- Chiba, Shunsuke,Ong, Derek Yiren,Pang, Jia Hao,Takita, Ryo,Watanabe, Kohei
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p. 393 - 398
(2020/01/23)
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- A Co-Cu bimetallic magnetic nanocatalyst with synergistic and bifunctional performance for the base-free Suzuki, Sonogashira, and C-N cross-coupling reactions in water
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A novel magnetically recyclable bimetallic catalyst was prepared by anchoring imidazolium moiety and PEG chains on Fe3O4 NPs and named as Fe3O4?PEG/Cu-Co. It was found to be a powerful catalyst for the Sonogashira, Suzuki, and C-N cross-coupling reactions in water as a green solvent without the need for any external base. Fe3O4?PEG/Cu-Co was well characterized with FT-IR, FE-SEM, TEM, VSM, EDX, ICP, UV-visible, CV, and XPS analyses. Optimum ranges of parameters such as time, temperature, and amount of catalyst were investigated by Design-Expert 10.0.7 software for C-C Suzuki, Sonogashira, and C-N cross-coupling reactions to find the optimum conditions. The catalyst was compatible with a variety of aryl halides and N-arenes and gave favorable coupling products with good to high yields for all of them. Hot filtration and Hg poisoning tests involving the nanocatalyst revealed the stability, low metal leaching, and heterogeneous nature of the catalyst. Reaction mechanisms were proposed by study of the UV-visible spectra in situ as well as hydroquinone tests during the progress of reactions. In situ XPS analysis was also used to study the reaction mechanism. To prove the synergistic performance of Co and Cu in the catalyst, its various homologues were synthesized and applied to a model reaction separately, and then their catalytic activities were investigated. Finally, the catalyst could be recovered from the reaction mixture simply, and reused for several cycles with a minimum loss in catalytic activity and performance.
- Allahresani, Ali,Kazemnejadi, Milad,Nasseri, Mohammad Ali,Rezazadeh, Zinat
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p. 10645 - 10660
(2020/09/18)
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- Metal-free late-stage C(sp2)-H functionalization of: N -aryl amines with various sodium salts
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Metal-free consecutive C(sp2)-X (X = Cl, Br, S, N) bond formations of N-aryl amines (cyclic, fused, carbamate, and aminium radicals) were achieved under mild conditions using [bis(trifluoroacetoxy)iodo]benzene (PIFA) and simple nonharmful sodium salts. This direct and selective C(sp2)-H functionalization showed excellent functional group compatibility, cost effectiveness, and late-stage applicability for the synthesis of biologically active natural products. Two mechanisms were proposed to explain the ortho- or para-preference, as well as the accelerating effect of CH3NO2
- Mudithanapelli, Chandrashekar,Kim, Mi-Hyun
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p. 450 - 464
(2020/02/03)
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- Practical direct synthesis of: N -aryl-substituted azacycles from N -alkyl protected arylamines using TiCl4and DBU
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A novel transformation of N-alkyl protected arylamines and cyclic ethers into N-aryl substituted azacycles is described. Alkyl groups have been used for the protection of amines in organic syntheses. In this synthesis, N-alkyl protected arylamines were reacted with cyclic ethers in the presence of TiCl4 and DBU, crucial reagents affording five- and six-membered azacycles. In particular, utilization of the novel TiCl4/DBU-mediated reaction allows various N-alkyl protected arylamines such as N-methyl-, N-ethyl-, N-isopropyl, and N-tert-butyl arylamines to be readily converted into N-aryl substituted azacycles in high yields. This practical approach using various N-alkyl arylamines leads to the efficient preparation of azacycles.
- Kang, Soosung,Kim, Hee-Kwon,La, Minh Thanh,Tran, Van Hieu
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p. 5008 - 5016
(2020/07/30)
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- Copper-Catalyzed Electrophilic Amination of Alkoxyarylsilanes
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We report a copper-catalyzed amination reaction between simple alkoxyarylsilanes and N-benzoyloxyamines. Silver fluoride serves as a stoichiometric base as well as an indispensable activator that allows the catalytic process to proceed. Multiply alkoxylated arylsilanes, such as trialkoxyarylsilanes and dialkoxyarylsilanes were transformed into the corresponding tertiary anilines under mild reaction conditions.
- Hitoshio, Kenshiro,Saito, Hayate,Shimokawa, Jun,Yorimitsu, Hideki,Zhang, Qian
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supporting information
(2020/07/04)
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- Copper(ii)-catalyzed c-n coupling of aryl halides and n-nucleophiles promoted by quebrachitol or diethylene glycol
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Herein, we report the natural ligand quebrachitol (QCT) as a promoter for a Cu(II) catalyst, which is highly effective for N-Arylation of various amines and related aryl halides. A series of diarylamine derivatives were obtained in high yields by using diethylene glycol (DEG) as both ligand and solvent. The C-N coupling reactions proceed under mild conditions and exhibit good functional group tolerance.
- Chen, Guoliang,Chen, Yuanguang,Du, Fangyu,Fu, Yang,Wu, Ying,Zhou, Qifan
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supporting information
p. 2161 - 2168
(2019/11/25)
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- C?N Cross-Coupling Reactions Under Mild Conditions Using Singlet Di-Radical Nickel(II)-Complexes as Catalyst: N-Arylation and Quinazoline Synthesis
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Herein we report a cost-effective synthetic approach for C?N cross-coupling reactions of a broad array of nitrogen nucleophiles and aryl halides under mild conditions. These reactions are catalyzed by an inexpensive, air-stable, earth-abundant and easy-to-prepare singlet di-radical nickel(II)-catalyst containing two antiferromagnetically coupled single-electron oxidized diiminosemiquinonato type ligands. This protocol provides an alternative method for C?N cross-coupling reactions avoiding nickel(0)/nickel(II) or nickel(I)/nickel(III) redox processes via cooperative participation of metal and ligand-centered redox events. Besides a wide range of N-arylation reactions, by judicious choice of aryl halides and nitrogen nucleophiles the synthesis of a variety of polysubstituted quinazolines has been achieved in moderate to good yields under relatively mild reaction conditions. Our catalyst has been found to be almost equally effective in quinazoline synthesis via C?N cross-coupling of (i) 2-bromobenzylamine with benzamide, and (ii) 2-bromobenzylbromide with amidine. Control experiments and DFT studies were performed to improve the understanding of the cooperative participation of ligand and metal (nickel)-centered redox events during oxidative addition/reductive elimination processes of the catalytic cycle and to shed light on the plausible mechanistic pathway of the C?N cross-coupling reactions. (Figure presented.).
- Sikari, Rina,Sinha, Suman,Chakraborty, Gargi,Das, Siuli,van Leest, Nicolaas Petrus,Paul, Nanda D.
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supporting information
p. 4342 - 4353
(2019/08/21)
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- Iron-Catalyzed/Mediated C-N Bond Formation: Competition between Substrate Amination and Ligand Amination
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Iron catalyzed carbon-nitrogen bond formation reactions of a wide variety of nucleophiles and aryl halides using well-defined iron-complexes featuring redox noninnocent 2-(arylazo)-1,10-phenanthroline (L1) ligands are reported. Besides substrate centered C-N coupling, C-N bond formation reactions were also observed at the ortho- and para-positions of the phenyl ring of the coordinated azo-aromatic scaffolds affording new tetradentate ligands, 2-N-aryl-(2-arylazo)-1,10-phenanthroline (L2), and tridentate ligands, 4-N-aryl-(2-arylazo)-1,10-phenanthroline (L3), respectively. Control experiments and mechanistic studies reveal that the complex [FeL1Cl2] (1) undergoes in situ reduction during the catalytic reaction to produce the monoanionic complex [1]-, which then acts as the active catalyst. The metal (iron) and the coordinated ligand were found to work in a cooperative manner during the transfer processes involved in the fundamental steps of the catalytic cycle. Detailed experimental and theoretical (DFT) studies were performed to get insight into the competitive substrate versus ligand centered amination reactions.
- Sinha, Suman,Sikari, Rina,Sinha, Vivek,Jash, Upasona,Das, Siuli,Brand?o, Paula,Demeshko, Serhiy,Meyer, Franc,De Bruin, Bas,Paul, Nanda D.
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p. 1935 - 1948
(2019/01/25)
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- New Insights into the Reaction Capabilities of Ionic Organic Bases in Cu-Catalyzed Amination
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The application of ionic organic bases in the copper-catalyzed amination reaction (Ullmann reaction) has been studied at room temperature, with sub-mol-% catalyst loadings, and with more challenging amines at elevated temperatures. The cation present in the base has been shown to have little effect on the reaction at standard catalyst and ancillary ligand loadings, whereas the choice of anion is crucial for good reactivity. A substrate scope carried out at room temperature with the best performing bases, TBAM and TBPM, showed both bases to be highly effective under these mild reaction conditions. Moreover, under sub-mol % catalyst loadings and room temperature conditions, TBPM gave good to excellent yields for a number of different amines and functionalized aryl iodides (14 examples). However, reactions involving more challenging amines gave little or no yield. By using more forceful conditions (120 °C) moderate to excellent yields of cross-coupled products containing more challenging amines was achievable using TBPM and to a lesser extent with TBAM. As part of this work a study on the stability of the organic bases at 120 °C was undertaken. TBAM is shown to decompose to give nBu3N and mono-butylmalonate at higher temperatures, and this can be correlated to a decrease in performance in the coupling reaction. The phosphonium cations in TBPM did not undergo analogous reactivity but were shown instead to experience some degree of deprotonation at the α-CH2 to generate phosphonium ylides. This however did not lead to a significantly degradation in the activity of the TBPM in the cross-coupling reaction.
- Lo, Quintin A.,Sale, David,Braddock, D. Christopher,Davies, Robert P.
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p. 1944 - 1951
(2019/02/19)
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- Plasma-Made (Ni0.5Cu0.5)Fe2O4 Nanoparticles for Alcohol Amination under Microwave Heating
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Amine N-alkylation is a process involved in the production of a wide range of chemicals. Here we describe the synthesis of well-defined (Ni0.5Cu0.5)Fe2O4 magnetic nanoparticles by plasma induction, and their successful application to amine N-alkylation using alcohols as coupling agents through a borrowing hydrogen pathway. Plasma induction allows precise morphology and size control over nanoparticle synthesis, while allowing the one-pot production of decagram quantities of material. Up to date, such nanoparticles have never been applied for organic reactions. By coupling high-end characterization techniques with catalytic optimization, we showed that small Cu(0) satellite nanoparticles played an essential role in alcohol oxidation, whereas both Ni and Cu were required for the last step of the reaction. Using elemental mapping, we demonstrated that catalyst deactivation occurred through a leaching/re-deposition mechanism of Cu and Ni. The reactions were conducted under microwave conditions, which exerted a positive effect on catalytic activity. Finally, the catalyst was active at low metal loadings (2 mol%) even on the gram-scale, and affording unprecedented TON for this reaction catalyzed by Ni/Cu bimetallic systems (19).
- Li, Alain You,Dumaresq, Nicolas,Segalla, Andréanne,Braidy, Nadi,Moores, Audrey
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p. 3959 - 3972
(2019/08/12)
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- Heterogeneous Catalytic Reduction of Tertiary Amides with Hydrosilanes Using Unsupported Nanoporous Gold Catalyst
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We have demonstrated that the unsupported nanoporous gold (AuNPore) was a green and highly efficient heterogeneous catalyst for the reduction of amides to amines using hydrosilanes as reductants. A variety of tertiary amides with a broad functional groups were reduced to the corresponding tertiary amines in the presence of 2 mol% of AuNPore and PheMe2SiH or (Me2SiH)2O under mild conditions. AuNPore catalyst was recovered by simple filtration and used for twelve times without any loss of catalytic activity. The AuNPore/hydrosilane system was also successfully applied to the hydrosilative reduction of sulfoxides and N-oxides. (Figure presented.).
- Zhao, Yuhui,Zhang, Sheng,Yamamoto, Yoshinori,Bao, Ming,Jin, Tienan,Terada, Masahiro
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supporting information
p. 4817 - 4824
(2019/10/28)
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- Fe3O4@SiO2-copper sucrose xanthate as a green nanocatalyst for N-, O- and S-arylation
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Formation of C(sp2)–X bonds was carried out using a Fe3O4@SiO2-copper(I) sucrose xanthate nanoparticle catalyst with the aid of the copper(I) xanthate moiety in the catalyst which was prepared from the reaction between sucrose and carbon disulfide through an alkaline medium via the traditional Zeise approach. Various techniques were employed for the characterization of these novel nanoparticles. Three sorts of heteroatoms, N, O and S, successfully underwent heteroatom arylation to produce secondary or tertiary amines, ethers and thioethers, respectively.
- Radfar, Iman,Kazemi Miraki, Maryam,Esfandiary, Naghmeh,Ghandi, Leila,Heydari, Akbar
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- Nickel-catalyzed N-arylation of amines with arylboronic acids under open air
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In this study, a well-defined, novel NHC-Ni complex was developed and used to catalyze the N-arylation of alkyl- and arylamines with arylboronic acids in a rare version of Chan-Lam coupling. Although the same coupling using copper catalysts has been widely studied, the nickel-catalyzed version is rare and normally requires 10–20 mol% catalyst loading. This novel NHC-Ni complex in combination with 4,4′-dimethyl-2,2′-bipyridine, however, proved to be an effective catalyst that lowered the required catalyst loading to only 2.0 mol%.
- Ando, Shin,Hirota, Yurina,Matsunaga, Hirofumi,Ishizuka, Tadao
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supporting information
p. 1277 - 1280
(2019/04/10)
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- Robust Buchwald-Hartwig amination enabled by ball-milling
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An operationally simple mechanochemical method for the Pd catalysed Buchwald-Hartwig amination of arylhalides with secondary amines has been developed using a Pd PEPPSI catalyst system. The system is demonstrated on 30 substrates and applied in the context of a target synthesis. Furthermore, the performance of the reaction under aerobic conditions has been probed under traditional solution and mechanochemical conditions, the observations are discussed herein.
- Cao, Qun,Nicholson, William I.,Jones, Andrew C.,Browne, Duncan L.
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supporting information
p. 1722 - 1726
(2019/02/20)
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- Practical and regioselective amination of arenes using alkyl amines
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The formation of carbon–nitrogen bonds for the preparation of aromatic amines is among the top five reactions carried out globally for the production of high-value materials, ranging from from bulk chemicals to pharmaceuticals and polymers. As a result of this ubiquity and diversity, methods for their preparation impact the full spectrum of chemical syntheses in academia and industry. In general, these molecules are assembled through the stepwise introduction of a reactivity handle in place of an aromatic C–H bond (that is, a nitro group, halogen or boronic acid) and a subsequent functionalization or cross-coupling. Here we show that aromatic amines can be constructed by direct reaction of arenes and alkyl amines using photocatalysis, without the need for pre-functionalization. The process enables the easy preparation of advanced building blocks, tolerates a broad range of functionalities, and multigram scale can be achieved via a batch-to-flow protocol. The merit of this strategy as a late-stage functionalization platform has been demonstrated by the modification of several drugs, agrochemicals, peptides, chiral catalysts, polymers and organometallic complexes.
- Ruffoni, Alessandro,Juliá, Fabio,Svejstrup, Thomas D.,McMillan, Alastair J.,Douglas, James J.,Leonori, Daniele
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p. 426 - 433
(2019/05/01)
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- The impact of the nature of amine reactants in the palladium catalyzed conversion of phenol to N-substituted anilines
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Anilines and cyclohexylamines are currently produced from fossil feedstocks. Phenol would be an attractive alternative feedstock that can be obtained from renewable resources. We herein clarify the influence of the amine on the course of the amination of phenol using a hydrogen borrowing strategy. Amines can in this case act as a reductant which can be dehydrogenated to initiate the partial hydrogenation of phenol which is required for the reaction to take place. The nature of the amine reactant can have a larger effect than the presence of additional reductants like sodium formate. The results in this report do not only present a method for the amination of phenol without addition of an extra reductant, but also rationalize the reactivity of amines in their reaction with phenol.
- Tomkins, Patrick,Valgaeren, Carlot,Adriaensen, Koen,Cuypers, Thomas,De Vos, Dirk E.
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p. 207 - 213
(2019/02/19)
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- “On Water” promoted N-arylation reactions using Cu (0)/myo-inositol catalytic system
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Myo-inositol is originally applied as a cardiovascular medicine in clinic, which can be multi-ton manufactured via extraction from the byproducts in agricultural product processing such as defatted rice bran and corn-soaking water. Herein, the application of myo-inositol (MI) as a novel versatile tridentate O-donor ligand has been first described for promoting Cu-catalyzed amination reaction in aqueous medium.
- Zhou, Qifan,Du, Fangyu,Chen, Yuanguang,Fu, Yang,Chen, Guoliang
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supporting information
p. 1938 - 1941
(2019/06/24)
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- α-d-Galacturonic Acid as Natural Ligand for Selective Copper-Catalyzed N-Arylation of N-Containing Heterocycles
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The first application of α-d-galacturonic acid hydrate (GalA) is reported here, as a potential O-donor ligand. The C-N couplings of N-heterocycles with aryl halides or arylboronic acids could be readily conducted and exhibited good functional group tolerance with characters of selectivity. These N-Arylazoles allow rapid access to several pharmaceutical intermediates and can be easily transformed into a variety of other interesting scaffolds as well.
- Yuan, Chunling,Zhao, Yingdai,Zheng, Li
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p. 2173 - 2180
(2019/11/25)
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- Facile synthesis of Pd(ii) and Ni(ii) pincer carbene complexes by the double C-H bond activation of a new hexahydropyrimidine-based bis(phosphine): Catalysis of C-N couplings
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Hexahydropyrimidine-based bis(phosphine), a pro-NHC ligand, was synthesized in one step and excellent yield. It underwent spontaneous double C-H bond activation to give cationic pincer NHC complexes of the type [(PCP)MCl]X (M = Pd, Ni and X = Cl, BF4) in the absence of any external reagents. Their structures were determined by X-ray diffraction methods and the mechanism of formation of palladium carbene complexes as analyzed by DFT calculations showed two transition states. The Pd(ii) carbene complex effectively catalyzes a few C-N cross coupling reactions.
- Subramaniyan, Vasudevan,Dutta, Bidisa,Govindaraj, Anbarasu,Mani, Ganesan
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p. 7203 - 7210
(2019/06/13)
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- Electrochemical Regioselective Bromination of Electron-Rich Aromatic Rings Using n Bu 4 NBr
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Electrochemical regioselective bromination of electron-rich aromatic rings using stoichiometric tetrabutylammonium bromide (n Bu 4 NBr) has been accomplished under mild conditions. This protocol provides an environmentally friendly and simple way for the construction of C-Br bond in moderate to high yields with wide functional group tolerance.
- Bai, Ya,Che, Xin,Liu, Nian,Ning, Shulin,Shi, Lingling,Wang, Shutao,Wang, Siyu,Xiang, Jinbao,Xie, Wenxia
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supporting information
p. 1313 - 1316
(2019/06/20)
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- PIFA-Promoted, Solvent-Controlled Selective Functionalization of C(sp2)-H or C(sp3)-H: Nitration via C-N Bond Cleavage of CH3NO2, Cyanation, or Oxygenation in Water
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A novel nitration (via C(sp3)-N breaking/C(sp2)-N formation with CH3NO2) mediated by [bis(trifluoroacetoxy)iodo]benzene (PIFA) is described. The NO2 transfer from CH3NO2 to the aromatic group of the substrate is possible with careful selection of the solvent, NaX, and oxidant. In addition, the solvent-controlled C(sp2)-H functionalization can shift to an α-C(sp3)-H functionalization (cyanation or oxygenation) of the α-C(sp3)-H of cyclic amines.
- Mudithanapelli, Chandrashekar,Dhorma, Lama Prema,Kim, Mi-Hyun
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supporting information
(2019/05/07)
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- Phosphoryl chloride-mediated solvent-free synthesis of N-aryl-substituted azacycles from arylamines and cyclic ethers
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A solvent- and metal-free protocol for preparation of N-aryl substituted azacycles from arylamines and cyclic ethers is described. In this method, the combination of POCl3 and DBU is crucial for conversion of arylamines and cyclic ethers to five- and six-membered azacycles. Without solvent, a variety of N-aryl-substituted, five-membered azacycles (pyrrolidines, 2-methylpyrrolidines, and piperidine) and six-membered azacycles (isoindolines and tetrahydroisoquinolines) are synthesized in high yields. This green method provides a sustainable and efficient approach for the preparation of azacycles from various cyclic ethers.
- Tran, Van Hieu,La, Minh Thanh,Kim, Hee-Kwon
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supporting information
p. 1860 - 1863
(2019/06/19)
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- Metal-Free Synthesis of N-Aryl-Substituted Azacycles from Cyclic Ethers Using POCl3
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A facile method for the synthesis of N-aryl-substituted azacycles from arylamines and cyclic ethers has been developed. In this study, arylamines were treated with cyclic ethers in the presence of POCl3 and DBU to provide five- A nd six-membered azacycles. Using this method, various azacycloalkanes, isoindolines, and tetrahydroisoquinolines were prepared in high yields. This synthetic method offers an efficient approach to the production of azacycles from cyclic ethers.
- La, Minh Thanh,Kang, Soosung,Kim, Hee-Kwon
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p. 6689 - 6696
(2019/06/14)
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- Reaction of Nitrogen-Radicals with Organometallics Under Ni-Catalysis: N-Arylations and Amino-Functionalization Cascades
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Herein, we report a strategy for the generation of nitrogen-radicals by ground-state single electron transfer with organyl–NiI species. Depending on the philicity of the N-radical, two types of processes have been developed. In the case of nucleophilic aminyl radicals direct N-arylation with aryl organozinc, organoboron, and organosilicon reagents was achieved. In the case of electrophilic amidyl radicals, cascade processes involving intramolecular cyclization, followed by reaction with both aryl and alkyl organometallics have been developed. The N-cyclization–alkylation cascade introduces a novel retrosynthetic disconnection for the assembly of substituted lactams and pyrrolidines with its potential demonstrated in the short total synthesis of four venom alkaloids.
- Angelini, Lucrezia,Davies, Jacob,Simonetti, Marco,Malet Sanz, Laia,Sheikh, Nadeem S.,Leonori, Daniele
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supporting information
p. 5003 - 5007
(2019/03/17)
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- Copper-Catalyzed NaBAr 4-Based N-Arylation of Amines
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Using NaBAr 4 as an arylating agent, the formation of carbon-heteroatom bonds by a Cham-Lam cross-coupling reaction in the presence of catalytic copper(II) acetate monohydrate in acetonitrile at room temperature under air is described. The investigation of reaction scope suggests that several aliphatic and aromatic amines are compatible. In particular, the reaction of alkylamine and NaBAr 4 proceeds smoothly to offer the corresponding products in good to excellent yields.
- Yang, Qin,Lei, Xiaoli,Yin, Zhijian,Deng, Zhihong,Peng, Yiyuan
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supporting information
p. 538 - 544
(2019/01/10)
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- Pyridyl Radical Cation for C?H Amination of Arenes
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Electron-transfer photocatalysis provides access to the elusive and unprecedented N-pyridyl radical cation from selected N-substituted pyridinium reagents. The resulting C(sp2)?H functionalization of (hetero)arenes furnishes versatile intermediates for the development of valuable aminated aryl scaffolds. Mechanistic studies that include the first spectroscopic evidence of a spin-trapped N-pyridyl radical adduct implicate SET-triggered, pseudo-mesolytic cleavage of the N?X pyridinium reagents mediated by visible light.
- R?ssler, Simon L.,Jelier, Benson J.,Tripet, Pascal F.,Shemet, Andrej,Jeschke, Gunnar,Togni, Antonio,Carreira, Erick M.
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p. 526 - 531
(2019/01/04)
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- Synthesis method for converting lignin 4-O-5 model compound diaryl ether into nitrogen-containing compound
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The invention discloses a synthesis method for converting lignin 4-O-5 model compound diaryl ether into a nitrogen-containing compound. According to the synthesis method, a diaryl ether compound andan amine compound are subjected to a heating reaction in a certain amount of a solvent (containing a certain amount of water) in an argon atmosphere (containing a certain amount of air) under the actions of a metal catalyst and sodium borohydride, such that the drug with the important physiological activity or the compound with the natural product skeleton containing nitrogen is formed by directlycoupling the C-O bond cut and the amine compound cross while the corresponding aromatic hydrocarbon is obtained. According to the present invention, the synthesis method has characteristics of simpleand easily-available raw materials, high conversion rate, important product and good yield, and has broad application prospects in the degradation and deep development and utilization of lignin.
- -
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Paragraph 0024-0026
(2019/04/26)
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- Palladium(II) anchored on polydopamine coated-magnetic nanoparticles (Fe3O4&at;PDA&at;Pd(II)): A heterogeneous and core–shell nanocatalyst in Buchwald–Hartwig C–N cross coupling reactions
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An efficient method was proposed to synthesize polydopamine (PDA)-coated Fe3O4 nanoparticles (Fe3O4&at;PDA). For the first time, effective deposition of Pd complex is explained by using Fe3O4&at;PDA as a core–shell magnetic coordinator and stabilizer agent. In this method, palladium ions were adsorbed on Fe3O4&at;PDA surfaces through immersion of the Fe3O4&at;PDA into a palladium plating bath. The structure, morphology and physicochemical features of the prepared particles were studied using various analytical methods including high resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDS), vibrating sample magnetometer (VSM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP), thermogravimetric analysis (TGA) and FT-IR spectroscopy. Core–shell Fe3O4&at;PDA/Pd(II) nanoparticles showed excellent catalytic performance as a reusable nanocatalyst in Pd-catalyzed Buchwald–Hartwig C–N cross coupling reaction. A variety of aryl amines were prepared through reaction of aryl halides (chloride, bromide and iodide) and amines in high yields. The catalyst can be recycled and reapplied up to six cycles with no considerable change in its catalytic activity.
- Hemmati, Saba,Sarachegol, Pegah,Veisi, Hojat
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- Ultrafine hybrid Cu2O-Fe2O3 nanoparticles stabilized by hexaphenylbenzene-based supramolecular assemblies: A photocatalytic system for the Ullmann-Goldberg coupling reaction
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Ultrafine hybrid Cu2O-Fe2O3 NPs have been prepared using the supramolecular assemblies of hexaphenylbenzene (HPB) derivative 3 as nanoreactors and stabilizers. The as-prepared hybrid Cu2O-Fe2O3 NPs serve as an efficient and recyclable photocatalytic system for carrying out C-N coupling between aryl halides and various amines (aliphatic, aromatic and N-heterocyclic) at room temperature in mixed aqueous media under visible light irradiation. Amazingly, Cu2O-Fe2O3 NPs also exhibited high efficiency in the reactions involving the synthesis of biologically important N-substituted carbazole derivatives. The work being presented in this article demonstrates the preparation of a 'dip strip' coated with the as-prepared catalytic system and utilization of this paper strip as a recyclable and portable heterocatalytic system for carrying out the Ullmann-Goldberg coupling.
- Singh, Gurpreet,Kumar, Manoj,Bhalla, Vandana
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p. 5346 - 5357
(2018/12/05)
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- A new diphosphine-carbonyl complex of ruthenium: an efficient precursor for C-C and C-N bond coupling catalysis
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Reaction of 1,2-bis(diphenylphosphino)benzene (dppbz) with [{Ru(CO)2Cl2}n] affords [Ru(dppbz)(CO)2Cl2], where the two carbonyls are mutually cis and the two chlorides are trans. The molecular structure of [Ru(dppbz)(CO)2Cl2], has been determined by X-ray crystallography, and the stability of the different available stereoisomers has been computationally evaluated. [Ru(dppbz)(CO)2Cl2] has been found to serve as an excellent pre-catalyst for catalytic Suzuki-type C-C coupling and Buchwald-type C-N coupling reactions.
- Mukherjee, Aparajita,Hrovat, David A.,Richmond, Michael G.,Bhattacharya, Samaresh
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p. 10264 - 10272
(2018/08/06)
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- Efficient nickel-catalysed: N -alkylation of amines with alcohols
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The selective N-alkylation of amines with alcohols via the borrowing hydrogen strategy represents a prominent sustainable catalytic method, which produces water as the only by-product and is ideally suited for the catalytic transformation of widely available alcohol reaction partners that can be derived from renewable resources. Intensive research has been devoted to the development of novel catalysts that are mainly based on expensive noble metals. However, the availability of homogeneous or heterogeneous non-precious metal catalysts for this transformation is very limited. Herein we present a highly active and remarkably easy-to-prepare Ni based catalyst system for the selective N-alkylation of amines with alcohols, that is in situ generated from Ni(COD)2 and KOH under ligand-free conditions. This novel method is very efficient for the functionalization of aniline and derivatives with a wide range of aromatic and aliphatic alcohols as well as diols and exhibits excellent functional group tolerance including halides, benzodioxane and heteroaromatic groups. Several TEM measurements combined with elemental analysis were conducted in order to gain insight into the nature of the active catalyst and factors influencing reactivity.
- Afanasenko, Anastasiia,Elangovan, Saravanakumar,Stuart, Marc C. A.,Bonura, Giuseppe,Frusteri, Francesco,Barta, Katalin
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p. 5498 - 5505
(2018/11/20)
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- Dual C(sp3)?H Bond Functionalization of N-Heterocycles through Sequential Visible-Light Photocatalyzed Dehydrogenation/[2+2] Cycloaddition Reactions
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Herein we describe a mild method for the dual C(sp3)?H bond functionalization of saturated nitrogen-containing heterocycles through a sequential visible-light photocatalyzed dehydrogenation/[2+2] cycloaddition procedure. As a complementary approach to the well-established use of iminium ion and α-amino radical intermediates, the elusive cyclic enamine intermediates were effectively generated by photoredox catalysis under mild conditions and efficiently captured by acetylene esters to form a wide array of bicyclic amino acid derivatives, thus enabling the simultaneous functionalization of two vicinal C(sp3)?H bonds.
- Xu, Guo-Qiang,Xu, Ji-Tao,Feng, Zhi-Tao,Liang, Hui,Wang, Zhu-Yin,Qin, Yong,Xu, Peng-Fei
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supporting information
p. 5110 - 5114
(2018/03/27)
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- Transition-Metal-Free Selective C?H Benzylation of Tertiary Arylamines by a Dearomatization-Aromatization Sequence
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Due to the significance of hybrid systems in drug discovery, there is an urgent need to assemble multiple biologically active ingredients into a single molecule. Here, we report a general transition-metal-free selective C?H benzylation of tertiary arylamines in good to excellent yields with a broad substrate scope and high functional-group tolerance under mild conditions. Besides arylamines, some other benzene derivatives also readily furnished the corresponding diaryl methane derivatives with this protocol. A series of control experiments and theoretical calculations indicated that this transition-metal-free reaction is a dearomatization-aromatization process.
- Xu, Guo-Qiang,Feng, Zhi-Tao,Xu, Ji-Tao,Wang, Zhu-Yin,Qin, Yong,Xu, Peng-Fei
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supporting information
p. 13778 - 13782
(2018/09/14)
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- Chan-Evans-Lam Couplings with Copper Iminoarylsulfonate Complexes: Scope and Mechanism
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Copper(II) pyridyliminoarylsulfonate complexes with chloride or triflate counteranions were employed in Chan-Evans-Lam (CEL) couplings of N-nucleophiles and arylboronic acids. The complexes avoided typical side reactions in CEL couplings, and an excess of boronic acid was not required. Water was tolerated, and addition of neither base nor other additives was necessary. Primary amines, acyclic and cyclic secondary amines, anilines, aminophenol, imidazole, pyrazole, and phenyltetrazole can be quantitatively arylated at either 25 or 50 °C with 2.5 mol % of the catalyst. Reaction kinetics were investigated in detail. Kinetic and spectroscopic studies provide evidence for the formation of unproductive copper-substrate complexes. Formation of an aniline-phenylboronic acid adduct was responsible for the zero-order dependence of reaction rates on phenylboronic acid concentration. Kinetic evidence indicates that the order of reaction steps is transmetalation, nucleophile coordination, and oxidation. Couplings performed poorly with electron-deficient arylboronic acids, due to a slower Cu(II)/Cu(III) oxidation in the catalytic cycle. Photoredox catalysis partially resolved this problem, but addition of copper acetate as an external oxidant proved to be more efficient.
- Hardouin Duparc, Valérie,Bano, Guillaume L.,Schaper, Frank
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p. 7308 - 7325
(2018/07/05)
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